batch reactor
DESCRIPTION
In this topic we have discussed working principle of a Batch Reactor. We've also discussed its kinetics like its Rate equation, Material and Energy balance. Its Design steps also have been discussed.TRANSCRIPT
Batch Reactor
M. Awais Yaqoob2011-ch-32
(University of Engineering and Technology, Lahore)
Mean residence time (t)
• It is taken as the measure of the performance of batch reactor
t =v/υ= volume of reactor Flow rate of feed in the reactor
SynopsisIntroduction
Working principle
Advantages and disadvantages
Applications
• Rate equation• Material balance• Energy balance
Kinetics
Design steps
Introduction
Working Principle
Advantages
limitations
1st Part
Material Balance
Performance Equation
Energy Balance
kinetics
2nd Part
Design steps
Factors
Design of BR
problem
3rd Part
Reactor DesignSize of reactor
• Fix one of the 5 parameter• Vf• Ws• S• Vs• Vr
• Shape• Spherical• cylindrical
• Dimensions• Internals• Inlets & outlets
Type of reactor
• BR• CSTR• PFR• Fixed bed
reactor• Fluidized
bed reactor• Slurry
reactor
Method of operation
• Batch• Continuou
s• Semi-
Continuous
• Intermittent
Method of OperationThermodynam
ic Basis
• Isothermal• Adiabatic• Constant
Volume• Constant
Pressure
Flow Patern
• Counter• Co Current• Cross
Current
Arrangment
• Series• Parallel• Recycle• Or
Combination Of Above
Introduction• The reactants are
initially charged into a container, are well mixed, and are left to react for a certain period.
• The resultant mixture is then discharged.
Working Principle• A batch reactor has neither inflow
nor outflow of reactants or products while the reaction is being carried out
• This is an unsteady-state operation where composition changes with time; however, at any instant the composition throughout the reactor is uniform
Advantages• They are preferred for establishing or
verifying kinetics because they are
o Simple in constructionoRequire little or no auxiliary equipments
• Data can be collected easily if Isothermal reactions are carried out under constant volume condition
• High conversions
Disadvantages/limitations• Intensity of process is localized and not
the global one• Preferred for homogenous reactions only• high labor costs per batch • difficulty of large-scale production.• Long idle time (Charging & Discharging
times) leads to periods of no production• No instrumentation – Poor product quality
Application• Typically for liquid phase reactions that
require long reaction times
• Used only when small amount of product is required
• Favored when a process is in developmental stage or to produce expensive products
• Used to make a variety of products at different times
Material Balance• Also called mass balance.• Is an application of law of
conservation of mass for the analysis of physical systems.
• It states that:• The mass that enters a system must,
by conservation of mass, either leave the system or accumulate within the system
Performance equation
(mA)in - (mA)out + (mA)gen - (mA)cons= (mA)acc/dep
since(mA)cons - (mA)gen = (mA)net cons
In case of BR(mA)in and (mA)out = 0The above equation will become-(mA)net cons = (mA)acc/dep
Dividing the above equation with molar mass of component A
• -(NA)net cons = (NA)acc/dep Since
After Substituting these values we will get
• Rearranging and integrating will give
Corollary• If the density of the fluid remains constant, we
obtain
Energy Balance• It is the application of law of conservation of
energy for the analysis of our physical system under consideration
• The heat that enters a system must, by conservation of heat/energy, either leave the system or accumulate within the system
• Overall energy balance
• heat in – heat out + heat gen – heat cons = heat acc/dep
KineticsRate Law For Zero Order Reaction
• Assumptions:o Isothermalo constant volumeo irreversible reaction
Stoichiometry:
Assumed rate law:
• Integrated rate law
Some Integrated rate equations
First order
Second order
Third order• Irreversible trimoleculer• A + B + D products
nth order
Design StepsFACTORS
• Type Of Reaction• Scale Of Prodution• Cost Of Equipment And Operations• Safety • Stability • Life Expectency• Ease Of Convertibility
Design steps• There is no particular formula for selecting the
parameters of a reactor
•Experience•knowledge of characteristics of reactors•literature surveyHelps us in selection of parameters
A Typical Batch Reactor
Design Measurements
Typical Proportions